Osiel Cárdenas Guillén, one of Mexico’s most feared and brutal drug lords, has been released from a U.S. prison after serving the majority of a 25-year sentence, U.S. authorities confirmed on Friday. The former leader of the notorious Gulf Cartel, known for his ruthless tactics and creation of the infamous Zetas hit squad, is now in the custody of U.S. Immigration and Customs Enforcement (ICE), potentially facing deportation to Mexico.

Cárdenas Guillén, 57, was sentenced in 2010 after his extradition to the United States in 2007. He had been convicted on charges related to drug trafficking and was ordered to forfeit tens of millions of dollars. His early release has raised questions, as the full details behind his shortened sentence have not been disclosed. Upon his return to Mexico, he is likely to be arrested, as he faces two outstanding arrest warrants in his home country, according to a Mexican official.

During his reign, Cárdenas Guillén turned the Gulf Cartel into one of the most powerful criminal organizations in Mexico, controlling vast cocaine shipments and amassing immense wealth. His most notorious legacy is the creation of the Zetas, a group of former Mexican special forces soldiers who became his private army and were known for their extreme violence. The Zetas terrorized Mexico with brutal acts, including mass killings and decapitations, and even after Cárdenas Guillén’s capture in 2003, they continued to spread fear across the country.

While the Zetas eventually splintered, with their top leaders being killed or captured by 2013, their influence persists in offshoots like the Northeast Cartel, which still controls key border regions. Meanwhile, the Gulf Cartel itself has fragmented into various factions, such as The Metros, The Cyclones, and The Scorpions, engaged in bloody internal conflicts.

Cárdenas Guillén’s infamy extends beyond his cartel activities; in 1999, he orchestrated a bold confrontation with U.S. Drug Enforcement Administration (DEA) agents in Matamoros, Mexico. His gunmen surrounded the agents, demanding the surrender of their informant. The standoff ended without bloodshed, but it cemented Cárdenas Guillén’s reputation for audacity, as he reportedly declared to the agents, “You gringos, this is my territory.”